[niku2803]

Can anybody suggest methods to analyze heavy metals like Pb, Cd, Hg, Cr, etc. in samples of KMnO4 powder?

Regards,
Nikunj

[Arkcon]

ICP, either ES or fluorescence.  You never asked how expensive the analytical instrument would be.   'Tho you may get poor results for Hg, depending on the sensitivity you need.  There are other spectrometric methods, if you need something more low rent.  Quantitative and qualitative wet chemical analysis is a long lost art, and probably now what you want to use when you have 4 or more impurities to look for.

[niku2803]

can you suggest something other than icp spectrometry? may be some other equipment or some older analysis method like quantitative and qualitative wet chemical analysis  ?

[Rabn]

I'll throw out an idea, you could make your sample aqueous and titrate with a chelating agent, or straight pH if the Ksp's are distinct enough, to selectively precipitate each metal.  Or you could use atomic absorption spectroscopy as long as you have the equipment.  You also may be able to use a UV/Vis spectrophotometer with a lot of work.  This website may help you out:  http://chemistry.about.com/library/weekly/aa091001a.htm

[kilroy]

It depend of the levels of heavy metals. I might suggest atomic absorbtion spectroscopy or XRF analysis. The XRF technique is a very nice and smooth way if you want to detect quite low levels of heavy metals.

[Train]

You might find USP <231> helpful.  It describes a limit test for the detection of heavy metals using a reaction with thioacetamide to form metal sulfide.

[marquis]

I would recommend staying away from USP<231>.  It is very nonspecific.

The method precipitates metal sulfides, which are all dark colored.  The method just measures the darkness.  It is compared to a lead standard, but in reality measures a relatively large number of metal sulfides.

Just a FYI on the method.